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42

ALUMINIUM ACETATE

8-719 grams of the bromide are dissolved separately in water and the two
solutions mixed and made up to i litre.

(&) I volume of cone, sulphuric acid, mixed with 3 vols. of water
and cooled.

The procedure is as follows : 100 c.c. of solution («) and 20 c.c. of solu-
tion (b) are mixed in a 100 c.c. flask and the methyl alcohol run in slowly
from a burette until the liquid appears colourless, the determination being
made in daylight and not in artificial light. The bromine absorption is
expressed by indicating the number of c.c. of methyl alcohol used.

8. Esters.—To 10 c.c. of the methyl alcohol mixed with 40 c.c. of water
and a few drops of phenolphthalein solution N/io-potassium hydroxide
solution is added until the liquid becomes pale pink. The liquid is then
boiled for 15 minutes with 20 c.c. of N-caustic soda, solution and, after
cooling, the excess of alkali is titrated with M-sulphuric acid. Multiplica-
tion of the number of c.c. of caustic potash absorbed in the saponification
by 0-74 gives the quantity of esters, calculated as .methyl acetate, in 100

c.c. of the alcohol.

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*  *

Methyl alcohol (-punas.) is a colourless, neutral liquid, with a pleasant odour
recalling that of ethyl alcohol, and shows at least 99° on the alcoholometer and
contains not more than ivi% of acetone. It should distil within 0*5° and the
sulphuric acid test should give only a slightly yellow liquid. It should not
decolorise permanganate immediately and should mix in all proportions with
water without opalescence and should ntix with concentrated caustic soda, solu-
tion without becoming coloured.

Commercial methyl alcohol (rectified, white methyl alcohol) is colourless or
only faintly yellowish, with a distinctive, stinging odour (not empyreuinatie) ;
its alcoholometric strength is 95-99°, its b.pt. (>.{ -1)7°, and as a, rule it contains
i--3% of acetone (some qualities used as solvents contain as much as 15 20%).

Crude methyl alcohol or wood spirit is a yellowish, liquid of einpyreuinatie
odour and burning taste, its alcoholometric strength being 90 -9I:0 ; it is not
completely soluble in caustic soda solution (,15-^0% separates), contains 15--25%
of acetone and distils to the extent of 90% between do" and 75°. Tho impurities
are principally acetone, methyl acetate, a'llyl alcohol, ammonia and pyridine
bases, empyreumatie products, etc,

Crude methyl alcohol to be used for the dcuaturation of alcohol must: satisfy,
in different countries, definite conditions as to colour, specific gravity, boiling
point, solubility in water and in caustic soda solution, acetone.* content, absorp-
tion of bromine and other less important characters.

ALUM—POTASSIUM  ALUMINIUM   SULPHATE
Ala(S04)3l KaS04 + 24Ha() ^ 949-2

Large, colourless, transparent crystals, which slowly effloresce in the
air, soluble in 10 parts of water, insoluble in alcohol. It is usually moder-
ately pure and it is usually sufficient to test it for iron and free* sulphuric
acid, as described under Aluminium Sulphate.

ALUMINIUM  ACETATE

For use in dyeing, normal aluminium acetate, Al(C2HaOa)8, the basic
acetate and various sulpho-acetates are sold, mostly in solution.

The impurities to be sought in these products are lead, zinc, iron, limehloric acid, should yield n,o free iodine. oxalic acid.                                            ^'--;'